LAUSR

Abstract Black phosphorus (BP) nanodots inevitably interact with electrolyte ions because of their extensive applications in many fields. In biomedical applications, BP-nanodots might encounter various salt ions in body fluids and have a propensity to aggregate, further resulting in an enhanced toxicity risk. In this study, the effects of electrolyte cations (Na+, K+, Ca2+, and Mg2+) on the aggregation kinetics of BP-nanodots were investigated by means of dynamic light scattering (DLS). The critical coagulation concentration values of BP-nanodots were determined to be 242.11 mM NaCl, 95.01 mM KCl, 1.92 mM CaCl2, and 5.88 mM MgCl2. Divalent cations accelerated aggregation of BP-nanodots because of the stronger surface charge screening and their bridging with oxidized phosphorus species (PxOy) available on BP-nanodot surfaces. Furthermore, the divalent cations may interact with PxOy to form insoluble complex coatings on the nanoparticle surface and shield the charge. After modification with PEG, BP-nanodots presented enhanced stability in the presence of 2.5 mM CaCl2. This work is of great significance for understanding the aggregation behaviors of ultrasmall nanoparticles such as BP-nanodots in electrolyte solutions and provides insight into their safety assessment associated with biomedical applications.